Strictly foundry codes. There are no records left for any of those. The only block numbers that will help ID will be when you see a large "59" cast into the top of the bell housing which indicates a 1945-48 block.
Seems to be a confusing engine. No AB casting on bell housing, has 59AB heads. Talked to Bob Tobin who redid the motor & he said it wal a L block and had a ford 4" crank and 3-5/16 bore stock pistons. I'm so confused.
You are looking for a 59 at rear, not the AB...the A and the B are codes based on HEAD part numbers. If not 59, and if a 24 stud, it needs to be identified from block characteristics...it may well be built from one of the various '39-'42-WWII 239 blocks. In US built engines the 59 is really the only one that is clearly marked... A long shot: Eyeball area at front p***enger side of block on top surface for a stamped (NOT cast) 99 in about 1/4" letters. That is a mark of '39-40 239's... Next look at where intake bolts on...if there is a cast surface that is slightly raised from the flat under manifold, essentially looking like the intake gasket but iron, that would be typical of '41-WWII blocks. The 3 5/16 bore and '49n type Merc crank are VERY common mods, and lots of piston companies made all sorts of pistons for that combo.
Bob Tobin is confused. If it doesn't have a big L on the bellhousing, it's not an L block. And Fords never came with a 4" crank, only Mercurys. And there is no such thing as a stock bore of 3-5/16".
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